A carrier lock is a restriction your network puts on a phone so it will only work with that network’s service. It is invisible day to day and only shows up the moment you try to use someone else’s SIM or eSIM — which, for most people, is the week they go abroad.
Check it before you buy anything.
On iPhone
Settings → General → About → Carrier Lock.
- “No SIM restrictions” — you are unlocked. Good to go.
- Anything else — the phone is locked to a carrier.
On Android
There is no single reliable path, because manufacturers word it differently. Try:
- Settings → About phone → Status → SIM status, looking for lock information
- Settings → Connections → SIM manager on Samsung
- Searching Settings for “lock”
If nothing is conclusive, ask your carrier directly. That is the only definitive answer on Android.
The practical test
If you have access to another SIM from a different network, put it in. If the phone connects and shows that network’s name, it is unlocked. If it demands an unlock code or shows “SIM not supported”, it is locked.
This does not work on eSIM-only phones with no tray, where the Settings check is your only route.
How to get it unlocked
Contact the carrier the phone was bought from. Most will unlock free once these are true:
- The device is fully paid for, whether outright or through a completed contract
- The account is in good standing
- Any minimum term has passed
Requirements vary by country — some regulators require carriers to unlock on request, others leave it to the contract.
It is not instant. Expect anywhere from a few hours to several business days. Start at least a week before you travel.
After unlocking
Some phones need a restart, or to have a different SIM inserted, before the change takes effect. On iPhone, re-check Settings → General → About → Carrier Lock and confirm it now reads “No SIM restrictions”.
What if it cannot be unlocked?
If the phone is still on contract or the carrier refuses, a travel eSIM is not an option on that handset. Your alternatives:
- Roaming on your existing plan — check the daily rate and fair-use cap first
- A portable Wi-Fi hotspot, rented at your destination
- A second, unlocked phone, if you have an old one lying around
An old unlocked handset with a travel eSIM makes a perfectly good data device even if you keep using your main phone for calls.
Two checks, one minute
Before buying any eSIM:
- eSIM hardware — is there an EID in Settings? See the compatibility list.
- Not carrier-locked — the check above.
Both pass, and the rest is straightforward.